1. Field of the Invention
The present invention generally relates to engines and pumps and, more particularly, to an engine or pump where flow can be controlled between a port and a crankcase chamber by means of a crankshaft rotary valve.
2. Description of Related Art
Crankshaft rotary valves are very common in most single cylinder 2-cycle engines. A rotary valve operates by communicating with an intake port and a crankcase chamber. As the piston moves up, air and fuel are drawn into the crankcase chamber through a passageway in the crankshaft and intake port. The crankshaft rotary valve then closes as the crankshaft rotates and the air-fuel mixture is then compressed by the downward movement of the piston. The intake timing is set by the channel in the crankshaft rotary valve.
The difficulty in building multi-cylinder 2-cycle engines using the current crankshaft rotary valve is that the crankshaft and crankcase are difficult to manufacture and assemble due to the crankshaft offsets and bearing surfaces between the crankcase and crankshaft. This requires that the crankcase vary in size to accommodate the bearing surfaces and crankshaft offsets that the piston connecting rods are connected to. By enlarging the diameter of the bearing surface of the crankshaft to a minimum of the stroke distance, the diameter of the crankcase can be one diameter throughout the engine to greatly simplify manufacturing and assembly.